Negotiators from Greece's creditors have begun arriving in Athens to start technical discussions on a third multi-billion euro bailout deal.

The European Commission said talks had already started, but a Greek government spokeswoman said that high-level talks would not begin until later this week.

Olga Gerovasili said that senior negotiating staff would only arrive in Athens on Thursday or later.

Negotiators were initially expected to arrive last week.

But Ms Gerovasili said there was "no reason" for the delay, adding it was up to Greece's creditors as to when talks began.

European Commission spokeswoman Mina Andreeva told a news briefing: "Teams from the institutions are already on the ground in Athens and work is starting immediately as we speak.

"Work has started, meaning that the institutions are talking to the Greek authorities."

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The talks come as it emerged former finance minister Yanis Varoufakis told a group of investors in London that a five-man team under his leadership worked on a contingency plan to create euro liquidity if the European Central Bank (ECB) cut off emergency funding to the Greek financial system.

'Plan B'

Greek newspaper Kathimerini reported Mr Varoufakis as saying in a phone call that a small team in the governing Syriza party had prepared plans to secretly copy online tax codes.

It said the "Plan B" was devised to allow the government to introduce a parallel payment system if the banking system was closed down, which would have seen the return of the drachma.

Mr Varoufakis said passwords used by Greeks to access their online tax accounts were to have been copied secretly and used to issue new Pin numbers for every taxpayer to be used in transactions with the state.

"This would have created a parallel banking system, which would have given us some breathing space, while the banks would have been shut due to the ECB's aggressive policy," Mr Varoufakis was quoted as saying.

In the same phone call, Mr Varoufakis accused German Finance Minister Wolfgang Schaeuble of being "hell-bent" on ensuring Greece left the eurozone.

He added that while the government had a Plan B, the difficulty was "to go from the five people who were planning it to the 1,000 people that would have to implement it".

"For that I would have to receive another authorisation which never came," he said.

Mr Varoufakis told the Daily Telegraph the quotes were accurate but accused the Greek press of trying to make it look as if he planned a return to the drachma from the start.

"The context of all this is that they want to present me as a rogue finance minister, and have me indicted for treason. It is all part of an attempt to annul the first five months of this government and put it in the dustbin of history," he told the paper.